1. Field of the Invention
The present invention generally relates to a fluid-filled type vibration damping device that exhibits vibration-damping effect based on fluid action of a non-compressible fluid sealed within its interior, and more particularly to a fluid-filled type vibration damping device wherein a partition member, which partitions a primary fluid chamber and an equilibrium chamber both having the non-compressible fluid sealed therein, having a partition rubber film disposed therein so that the partition rubber film partially define the pressure receiving chamber; and wherein an air chamber is formed for restricting or allowing deformation of the partition rubber film.
2. Description of the Related Art
A fluid-filled vibration damping device is known as one type of vibration damping coupling and vibration damping support for installation between members constituting a vibration transmission system, such as an automotive engine mount or body mount. This fluid-filled type vibration damping device includes: a first mounting member and a second mounting member disposed apart from one another and linked by a rubber elastic body; a primary fluid chamber having part of its wall constituted by the rubber elastic body and having a non-compressible fluid sealed therein; an equilibrium chamber formed on the opposite side from the primary fluid chamber with a partition member supported on the second mounting member situated therebetween, whose wall is partially defined by a flexible film and having a non-compressible fluid sealed therein; and an orifice passage formed in the partition member through which the primary fluid chamber and the equilibrium chamber communicate with one another so that vibration damping effect is produced on the basis of flow action of the fluid flowing through the orifice passage.
As taught in JP-B2-2843088 and JP-A-4-277341 for example, there has also been proposed a construction in which a rubber elastic film constituting another part of the wall of the primary fluid chamber is disposed on the partition member, and a working air chamber is formed on the opposite side of the rubber elastic film from the primary fluid chamber. This vibration damping device has vibration damping characteristics that can be adjusted, for example, by controlling the air pressure exerted on the working air chamber to adjust the spring characteristics of the rubber elastic film, or by exerting pressure fluctuations on the air chamber to vibrate the rubber elastic film.
In a fluid-filled type vibration damping device of this kind having an air chamber disposed in its interior, it is important for there to be an adequate seal in the area where the partition member and the rubber elastic film are attached, so as to prevent the air in the working air chamber from entering into the fluid, or to prevent fluid from leaking from the primary fluid chamber or orifice passage through the area where the partition member and the rubber elastic film are assembled.
To address this matter, JP-U-5-77642, for example, has proposed a construction wherein the partition member has an interlocking structure composed of several members, these members being superimposed in the axial direction so as to sandwich the outside peripheral edges of the rubber elastic film, thereby holding the rubber elastic film clamped therebetween in the direction of superimposition by the partition member. In yet another structure as proposed in JP-A-11-264436, an engaging portion projects from the peripheral edge of the opening of the working air chamber, a round tubular metal fitting member is bonded by vulcanization about the outside peripheral edge of the rubber elastic film, and the tubular fitting member is externally fitted onto the engaging portion with a seal rubber layer formed on the inner circumferential surface of the tubular fitting member sandwiched therebetween, and subjected to a drawing process.
However, numerous experiments and extensive studies carried out by the inventors have revealed that, in the fluid-filled type vibration damping devices taught in JP-U-5-77642 and JP-A-11-264436 cited previously, seal performance in the area where the partition member and the rubber elastic film are attached is not yet sufficiently consistent and reliable.
In particular, in fluid-filled type vibration damping devices of conventional structure, including those taught in the four documents cited previously, when the partition member is inserted into the tubular second mounting member and the second mounting member is subjected to the drawing process from the outside in the diametrical direction, with the object of ensuring fluid-tightness in the primary fluid chamber, a gap tends to form in the area of attachment of partition member and the rubber elastic film disposed on the inside of the rubber elastic film. That is, since the shape and wall thickness dimension of the partition member are not uniform in the circumferential direction due to factors such as the shape and size of the orifice passage formed in the partition member, when in association with the drawing process compressive force is exerted by the second mounting member on the partition member, and on the tubular fitting member, irregular deformation tends to be produced in the partition member and the tubular fitting member, and the outer circumferential surface of the partition member abuts tightly against the seal rubber layer formed covering the inner circumferential surface of the second mounting member. Thus, the axially superimposed members that make up the partition member are supported in a floating state on the second mounting member, and the members tend to become eccentric to one another during the drawing process. As a result, a gap tends to form between the rubber elastic film and the partition member, through which gap air escaping from the working air chamber can become entrained in the fluid, or the orifice passage can become short circuited, making it difficult to obtain the desired vibration damping characteristics.